Comparison of the quantum dynamics and sensitivity analysis for different isotopomers of the H+H2 reaction

Non-Born-Oppenheimer dynamics calculations using the coherent switching with decay of mixing method

A theoretical investigation of the nonadiabatic processes that are involved in the full three-dimensional D+H(2), H+D(2), D(+)+H(2), and H(+)+D(2) reaction systems has been performed using the method of coherence switching with decay of mixing (CSDM) developed by Truhlar and coworkers. The electronic density matrix for each trajectory is fully coherent in the CSDM method, and a switching algorithm different to the original "decay of mixing" method is used to determine the pure state toward which the decoherent force drives the system. By solving the equations for the evolution of the electronic state populations along the semiclassical trajectory, the ensemble can present effective physical insight into nonadiabatic dynamics. The calculations for the D+H(2) and H+D(2) systems is based on the double many body expansion potential energy surface. The potential energy surface constructed by Kamisaka et al. is employed in the calculation of D(+)+H(2) and H(+)+D(2) reactions. The cross sections and the reaction probabilities for the total angular momentum J = 0 are calculated for all of these systems. The calculated results from the CSDM method are in good agreement with exact quantum mechanical calculations and experimental measurements.

Nonadiabatic effects in the H+D2 reaction

The state-to-state dynamics of the H+D2 reaction is studied by the reactant-product decoupling method using the double many-body expansion potential energy surface. Two approaches are compared: one uses only the lowest adiabatic sheet while the other employs both coupled diabatic sheets. Rotational distributions for the reaction H+D2 (upsilon = 0, j = 0)-->HD(upsilon' = 3, j')+D are obtained at eight different collision energies between 1.49 and 1.85 eV; no significant difference are found between the two approaches. Initial state-selected total reaction probabilities and integral cross sections are also given for energies ranging from 0.25 up to 2.0 eV with extremely small differences being observed between the two sets of results, thus showing that the nonadiabatic effects in the title reaction are negligible at least for small energies below 2.0 eV.